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Physics, Astronomy & Cosmology / Re: Is the radioactive decay dice experiment inaccurate?

« on: 01/03/2018 11:01:39 »

It's not the 1/6, you could do it with 1/12 sided dice and get same problem.
If I remember correctly you throw lots of dice and count 6s and say that is decay in 1s. It's the 1s that's the problem, during this time the real decay has been going on continuously from time 0.
It's a bit like compound interest in reverse, work it out in 1 year blocks or 1 month blocks and you get different answers.

EDIT: Whoops message collided with Alan's. Different way of calculating the granularity but same result.

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Physics, Astronomy & Cosmology / Re: Is the radioactive decay dice experiment inaccurate?

« on: 01/03/2018 11:01:23 »

Its "accuracy", i.e. the closeness of fit  to an actual decay curve, depends on the number of dice involved. If you start with 400 dice and eliminate all the 4,5 or 6 scores on each roll, the expectation* is that you will have 200, 100, 50 and 25 dice after 1,2,3 or 4 rolls. Problem is that the dice are entirely independent, so whether you have 12 or 13 after the next roll is a matter of chance. If you have 12, then subsequent rolls will  probably show a faster "decay", and 13 will show a slower decay than the expected rate.

If you want to simulate the decay of 1 gram of, say, ⁴⁰K, you will need 1.5 x 10²² dice (and roll them every 1.25 billion years, for complete realism!)


*Note that this is the central value of a random number. Things could go spectacularly "wrong" if the first roll left 190 or 210 rather than 200 dice, but the probability of doing so is quite high.

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Physics, Astronomy & Cosmology / Re: Is the radioactive decay dice experiment inaccurate?

« on: 01/03/2018 10:52:22 »

I think the biggest problem is getting enough dice (incidentally, dice is the plural- one, on its own, is a die).
Also, the dice get thrown in batches, but decay is continuous.

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Chemistry / Re: What is the formula to find ABV% in wine?

« on: 26/02/2018 10:29:39 »

ABV= (starting sg)- ( final sg)/(final sg) * 100

Don’t recognise this. Looks like a bit missing, I would expect to find a fractional multiplier ie divider, for the rhs equation

Got it from here. http://www.brewstore.co.uk/wp/wp-content/uploads/2014/04/taking-a-hydrometer-reading-and-calculating-the-alcohol-content-1.pdf

You've missed out the fraction multiplier 1.05/0.79

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Chemistry / Re: How do winemakers measure their grapes/must pH level?

« on: 23/02/2018 14:46:46 »

As an amature winemaker I used indicator papers or titration. For a different purpose I bought an electronic pH meter and i would have thought this is what professional makers use.

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Chemistry / Re: Is wines 2nd fermentation and malolactic fermentation the same thing?

« on: 21/02/2018 08:49:19 »

No, it is the conversion of malic acid to lactic acid which tastes better. It can be a secondary fermentation or part of the primary but it is a bacterial action so not part of any primary or secondary yeast fermentation.

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Chemistry / Re: How can pH be adjusted by using CaCO3 - calcium carbonate?

« on: 17/02/2018 16:07:11 »

i came across a simple one involving CaCO3. What are the steps for this procedure and how does it chemically work?

To answer this bit of the question, CaCO₃ is limestone. It has the ability to react with protons (hydrogen ions) to raise pH according to the reaction:

CaCO_3(s) + H⁺ → CO_2(g) + H₂O_(l) + Ca⁺⁺_(aq)

In effect, the calcium carbonate is soaking up the hydrogen ions that are the "acid" in a solution and thereby raising the pH.

You can see this reaction in action every time you de-scale your kettle with some citric acid.

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Chemistry / Re: How can pH be adjusted by using CaCO3 - calcium carbonate?

« on: 16/02/2018 17:23:54 »

What other simple chemical experiments are there used to alter pH of grapes?

If you add MgCO₃ or Mg(OH)₂ instead of CaCO₃, it helps you feel less muscular fatigue: athlets take sources of Mg²⁺ for that purpose  I don't know which will be the wine  final taste, however...

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Chemistry / Re: How can pH be adjusted by using CaCO3 - calcium carbonate?

« on: 16/02/2018 11:20:33 »

What other simple chemical experiments are there used to alter pH of grapes?

CaCO3 or limestone will work. Make sure to grind the CaCO3 to a powder so it can work faster. You can also use over the counter antacids containing sodium bicarbonate. However, if you are making wine, the yeast win't perform properly when the pH level gets too high.